Wednesday, July 23, 2014

New paper finds 23% of warming in Europe since 1980 due to clean air laws reducing sulfur dioxide

A paper published today in Geophysical Research Letters finds that clean air laws which greatly reduced sulfur dioxide emissions explain 81% of the "brightening" of sunshine and 23% of the surface warming in Europe since 1980. However, the authors note "this phenomenon is however hardly reproduced by global and regional climate models."

According to the paper,

"observed surface solar radiation, as well as land and sea surface temperature spatio-temporal variations over the Euro-Mediterranean region are only reproduced when simulations include the realistic aerosol variations" which the authors state are "however hardly reproduced by global and regional climate models"

Since the 1980s anthropogenic aerosols have been considerably reduced in Europe and the Mediterranean area. This decrease is often considered as the likely cause of the brightening effect observed over the same period. This phenomenon is however hardly reproduced by global and regional climate models. Here we use an original approach based on reanalysis-driven coupled regional climate system modelling, to show that aerosol changes explain 81 ± 16 per cent of the brightening and 23 ± 5 per cent of the surface warming simulated for the period 1980–2012 over Europe. The direct aerosol effect is found to dominate in the magnitude of the simulated brightening. The comparison between regional simulations and homogenized ground-based observations reveals that observed surface solar radiation, as well as land and sea surface temperature spatio-temporal variations over the Euro-Mediterranean region are only reproduced when simulations include the realistic aerosol variations.

to quantify the effect, a similar method shows Mt P. caused about 1.8 W/m2 change in incoming SW.http://climategrog.wordpress.com/?attachment_id=955

Estimating from the TLS data in that article, that El Chichon was of similar magnitude that makes about 3.5 W/m2. That is about the same as the current IPCC estimation for the radiative effect of CO2 doubling.

I continue to believe TOA radiative imbalances have little effect on surface temperatures, however, since convection dominates over radiation as the primary heat transfer mechanism in the troposphere and can easily compensate for surface warming or radiative imbalances at the TOA

Did you read the links? In particular this one, which is a detailed look at the data and the tropical climate reaction to a major radiative change:http://climategrog.wordpress.com/?attachment_id=884

What it shows is that volcanic forcing is a lot stronger than the values currently used. The corollary of this is that (tropical) climate is a lot less sensitive to radiation imbalance.

A key point is, the extra incoming is SW. This will penetrate directly into sub-surface waters and largely bypass the evaporative feedbacks at the surface.

Extra-tropical climate does not have such strong feedbacks. As I discussed in that article, part of that extra energy into the tropics will be communicated to neighbouring regions by the ocean gyres.

A very similar effect to the TLS changes can be found in SH SST.http://climategrog.wordpress.com/?attachment_id=988

There's more climate "noise" in the surface data and the oceans take a few years to respond but overlaying the two seems to show the same process affecting both.

Incident IR only heats the surface skin of the ocean and so very rapidly is lost to evaporation. The same is not true of SW. What I have demonstrated is about 1.8W/m2 of extra SW after Mt.P and presumably as much for El Chichon.

This ties in with the french study you picked up too.

They are basically saying the same thing but attribute the changes to emission controls.

I have clearly shown it correlated to the volcanic events.What probably happened is that the natural processes that flushed out the volcanic aerosols ended up scrubbing a lot of anthropogenic pollution too.